For Wiisx use Mod04b (It uses IOS58, which is an official IOS that supports USB 2.0), and make sure that you're config files/bios/savestates etc are all being loaded from the same place (USB) because the wii has a tough time trying to read from the USB while writing to SD, and emulating a game all at the same time.

Having everything set to load from the USB (Not the app itself, just the save/memcard/game/config/bios) has fixed every problem I've had with it, and it's much faster.

Still can't wait for a goddamned official update from the emulatemii team though.